Piston for internal combustion engine

ABSTRACT

This specification discloses a cooling system for a piston formed of two parts and joined by brazing within annular grooves. Passages for cooling fluids are conveniently formed before the separate pieces are joined and are positioned such that the high temperature at common joined areas is effectively limited to prevent temperature deterioration of the bond between the two joined pieces. In addition, the cooling fluid transfers heat away from a head portion of the piston and means are provided to utilize as a cooling fluid a lubricating fluid normally present at a pin-bearing surface of the piston.

1,763,625 6/1930 Mellor Inventor Takumi Itano Tokyo, Japan Appl. No. 862,422

Filed Sept. 30, 1969 Patented Oct. 19, 1971 Assignee Komatsu Manufacturing Co., Ltd.

Tokyo, Japan Priority Nov. 7, 1968 Japan 43/8092] PISTON FOR INTERNAL COMBUSTION ENGINE 4 Claims, 3 Drawing Figs.

US. Cl

Field of Search References Cited UNITED STATES PATENTS 2,407,429 9/1946 Kuttner 92/157 X 2,442,408 6/1948 Graham 123/4138 2,759,461 8/1956 Maybach et a1. 123/4135 3,215,130 11/1965 Maier 123/4135 3,354,793 11/1967 Meier et 81... 123/4135 X 3,380,556 4/1968 Whitehead 92/157 X 3,385,175 5/1968 Meier et a1... 92/186X 3,465,651 9/1969 Tromel 92/186 Primary ExaminerMartin P. Schwadron Assistant Examiner1rwin C. Cohen Attorney-Cushman, Darby & Cushman ABSTRACT: This specification discloses a cooling system for a piston formed of two parts and joined by brazing within annular grooves. Passages for cooling fluids are conveniently formed before the separate pieces are joined and are positioned such that the high temperature at common joined areas is effectively limited to prevent temperature deterioration of the bond between the two joined pieces In addition, the cooling fluid transfers heat away from a head portion of the piston and means are provided to utilize as a cooling fluid a lubricating fluid normally present at a pin-bearing surface of the piston.

PAIENIEDum 19 I97! SHEET 18F 2 Raw material INVENT OR F 0 RI 0 a 2 2 I Eo\9: 3976 2 :2

Test temperature (C) ZZ KdM/ [IA/V0 W 4 M f A'ITORNEYs PATENTEDHB 1 l9?! 3.613.521

SHEET 2 EF 2 Fig. 2

INVENTOR .ZEKMW/ Ira/v0 PISTON FOR INTERNAL COMBUSTION ENGINE The present invention relates to a split-type internally cooled piston for internal combustion engines, and more particularly, the structure of the piston wherein the upper and lower portions are integrally joined by brazing.

As is generally known to those skilled in the art the recent internal-combustion engines have a tendency of high speed and the highly excessive feeding of fuel and therefore the heat calories expended within the cylinder is added and increased when compared with the heat discharging area, and therefore not only the cooling of the cylinder, but also the cooling of the reciprocating piston must be taken into consideration.

On the other hand, the usual piston is designed to minimize inertia in a high-speed engine and therefore to also satisfy the above-mentioned heat dissipation demands, an upper portion of the piston is usually made of a heat-resistant steel, and the lower portion thereof is made of aluminium alloy, and the joined portion of the two contains cooling canal, and the two portions are connected with bolt or screw, as is generally known.

However, the heat-resistant steel of the pistons of such a structure gravity and the heat conductivity thereof is smaller than that of aluminium alloy, and therefore the reduction of the weight of piston has natural limitation, and the discharge of heat cannot be effectively carried out, and there is a fear that the piston-supporting portion should be loosened through the usage.

Thus, in order to remove the drawbacks of the above mentioned pistons, there has been proposed such counter measures as to cast the whole piston with aluminium alloy, and in the casting process the cooling canal is cast out, but there are difficulties in the selection of the meltable core to be used in the formation of the canal, and in the maintenance of the dies, and the cost of production thereof is high, and there are such like problems.

The object of the present invention is to provide a piston having the brazen structure adopted for using alumium alloy, and the piston of this invention comprises two portions divided along a plane rectangular to the axis thereof and forming a joining surface, i.e., an upper half head portion and a lower half skirt portion. The upper half head portion is formed with an annular cooling canal exposed to the joining surface and extending around the axis of the piston, thereby to form a plurality of annular lands at the joining surface. On the other hand, the joining surface of the lower half skirt portion is formed with a plurality of shallow annular grooves adapted to accommodate the joining surface of the upper half head portion therein. The upper half and lower half portion can be integrally joined by filling a brazing material into the annular grooves and then fitting the annular lands into corresponding annular grooves.

BRIEF EXPLANATION OF THE DRAWING:

FIG. I is the cross-sectional view of the piston of the present invention;

FIG. 2 is the cross-sectional view at a point 90 away in the peripherical direction of FIG. 1; and

FIG. 3 is a diagram showing the temperature characteristic of the tensile strength of Y alloy and aluminum raw material.

The following are the explanations about an embodiment of the piston for internal-combustion engine of the present invention.

The piston shown in FIG. I and FIG. 2 is provided with the upper half head portion 2 made of aluminum alloy having the combustion chamber 1, and the lower half skirt portion 3 made of aluminum alloy having been separately prepared from the half of the head portion 2.

The upper half head portion 2 is mechanically processed in such a manner that in the casting process the annular cooling canal 5 formed on the joined surface 4, and the half spherical return chamber 6 inside the cooling canal, are cast, or the cooling canal 5 and return chamber 6 are mechanically processes in the preparatory processing after casting. In regard to the interval between said cooling canal 5 and the return chamber 6, they are connected by a plurality of radial form return paths 7, 7, 7,

On the other hand, the lower half skirt portion 3 is produced in such a manner that the cavity 8 whose bottom is opened can be included, and on the side of the hole of the pin hole 9 into which the piston pin (not shown) is inserted, the oil groove 10 for supplying the cooling oil is provided by the cooperation of the piston pin, and said oil groove 10 is connected to the above mentioned cooling canal by means of the hole 12 which opens at the joined surface 11 On the other hand, in the center of the top surface of the half of the skirt portion 3, the outlet hole 13 for connecting said cavity 8 and said return chamber 6 of the upper half head portion 2, is provided, and the return oil is turned back to the lubricant oil chamber from said outlet hole 13.

On the other hand, on the joint surface 30 of the top surface of the half of the skirt portion 3, two lines of ring form grooves 14a and 14b for receiving said annular lands 2a and 2b are provided at the position corresponding to the annular land's 2a and 2b surrounding the inside and outside of the opening of said cooling canal 5.

Thus, on the inside and outside of the annular grooves [4a and 14b, the lands 15a, 15b and 150 for diving said ring form grooves 14a and 14b are formed.

Thus, in order to join the upper half head portion 2 and the lower half skirt portion 3 in the preparatory process, the two half portions are heated in an oven, and then a brazing matcrial 16 is filled and melted in said annular grooves and 14b.

In this case, when the lower half skirt portion 3 is kept horizontal, a brazing material 16 in the respective ring form grooves 14a and 14b is uniformly distributed all over the bottom of the grooves.

Thus, when the annular lands 2a and 2b of the half of the head portion 2 are agreed against the annular grooves 14a and 14b, the upper half head portion 2 and the lower half skirt portion 3 are correctly joined.

As is shown in FIG. 3, in regard to the tensile strength of Y alloy or aluminium alloy or such like joining materials to be used as raw material, it has the tendency to be lowered from about 200 C., but in the piston structure of the present invention, the mechanical strength of the joined portion is not lowered by the elevation of temperature.

Namely, the annular grooves 14a and 14b in which a brazing material 16 is filled, are placed in the down stream of the cooling canal 5, and therefore the heat received in the direction of the combustion chamber I of the upper half head portion 2 is effectively heated as the cooling canal 5, and the joined surface portion cannot be over heated.

On the other hand, the lubricant oil supplied into thc cooling canal 5, stays at the bottom of the cooling canal 5, and it is moved by the movement of the piston, and therefore the heat conductivity is high, and the lubricant oil in the canal 5 is turned into the return chamber 6 from the paths 7, 7, 7,.... along with the movement of the piston, and it is let out through the outlet hole 13 from said return chamber 6.

In accordance with the present invention, the upper half head portion is formed with an annular cooling canal exposed to the joining surface and extending around the axis of the piston, thereby to form a plurality of annular lands at the joining surface, and the annular lands are used as brazing surfaces. Therefore, the surfaces to be joined by brazing can be cooled by the cooling oil circulating through the adjacent cooling canal. Thus, it is possible to maintain the surfaces joined by brazing at a low temperature as nearly same as that of the cooling oil (below 12 C.

The joining by brazing is made by filling a brazing material into the shallow annular grooves of the lower half skirt portion and then fitting the annular lands into said grooves, so that there does not occur any wasteful flow-out of the brazing material and it is possible to distribute the molten brazing material and it is possible to distribute the molten brazing material evenly in the annular grooves and permit the flux to flow out in one direction so as to ensure complete and robust brazing. In this way, it becomes possible to obtain a strong and robust piston for internal-combustion engines which is joined by brazing.

What is claimed is: 1. An internally cooled piston for internal combustion engines, said piston comprising:

two portions divided to form joining surfaces separating an upper half portion and a lower half skirt portion, said upper half head portion being formed with an annular cooling canal exposed to the upper joining surface of said upper portion and extending around the axis of the piston and formed with a plurality of annular lands at the upper joining surface radially inwardly spaced from the outer periphery of the piston, and said lower half skirt portion being formed with a plurality of shallow annular grooves radially inwardly spaced from from the outer periphery of the piston at the lower joining surface which accommodate the plurality of annular lands of the upper joining surface of the-upper half head portion therein,

said shallow annular grooves being filled with a brazing material to braze said upper half head portion with said lower half skirt portion.

3 2. A piston as in claim I wherein said upper half head por tion is formed with a central void and means to provide fluid communication with said annular cooling canal.

3. A piston as in claim 2 which is normally lubricated with oil and including:

spherically shaped and said means providing fluid communication are holes. 

1. An internally cooled piston for internal combustion engines, said piston comprising: two portions divided to form joining surfaces separating an upper half portion and a lower half skirt portion, said upper half head portion being formed with an annular cooling canal exposed to the upper joining surface of said upper portion and extending around the axis of the piston and formed with a plurality of annular lands at the upper joining surface radially inwardly spaced from the outer periphery of the piston, and said lower half skirt portion being formed with a plurality of shallow annular grooves radially inwardly spaced from from the outer periphery of the piston at the lower joining surface which accommodate the plurality of annular lands of the upper joining surface of the upper half head portion therein, said shallow annular grooves being filled with a brazing material to braze said upper half head portion with said lower half skirt portion.
 2. A piston as in claim 1 wherein said upper half head portion is formed with a central void and means to provide fluid communication with said annular cooling canal.
 3. A piston as in claim 2 which is normally lubricated with oil and including: means for diverting a portion of said oil to the annular cooling canal to serve as a cooling fluid therein, and means for removing oil from said central void which has been passed thereto from said annular cooling canal.
 4. A piston as in claim 3 wherein said central void is hemispherically shaped and said means providing fluid communication are holes. 